The application proposes to be a collaborating clinical center in the Non-insulin-dependent diabetes (NIDDM) Primary Trial. Working on a Steering Committee, we will help design the trial and Operations Manual in Year 01, implement it in Years 02-06, and close it in Year 07. The enormity of the NIDDM problem, rationale for primary prevention, and specific background are reviewed. Eligibility will be determined by the presence of impaired glucose tolerance, a history of gestational diabetes mellitus, or previously undiagnosed mild (FPG less than 140 mg/dl) NIDDM. Recruitment of more than 200 subjects randomized will be accomplished by proven methods of community screening and mailings, in large employment and population centers, targeting more than 50% African-American subjects. The trial will be implemented in an existing facility (Hopkins ProHealth) designed and staffed specifically for the implementation of large, multicenter, NIH-supported clinical trials. A faculty with wide diversity of expertise in clinical diabetes, epidemiology, behavioral change, exercise, diet and community intervention strategies and assessment will take part in study development and implementation; an expert staff is already in place at ProHealth, including a Study Coordinator, Recruiters, Interventionists and Data Collectors, will implement the study on a daily basis. Based on preliminary biostatistical considerations, a 3-arm trial is proposed, comparing intensive life style changes (diet and increased activity) with a pharmacologic arm (sulfinylureas) and a placebo are. The proposed primary outcome measure is incidence of NIDDM with FPG greater than 140 mg/dl; secondary outcome measures include a stepped deterioration of glucose tolerance, cardiovascular risk factors associated with NIDDM, quality of life measures, cost, and morbidity/mortality. Intervention strategies and visit schedules are outlined. Assuming a placebo-group event rate of 5% to 10% per year, two intervention groups will detect a 22% to 30% effect of interventions. In sum, this is a strong faculty and staff with extensive experience, an up-and-running clinical trials facility ready to take part in the collaborative effort of designing and implementing this primary prevention trial.